/**
 * Implements hook_comment_insert().
 *
 * Send a message when a new comment is created to subscribed users.
 */
function dc_subscribe_comment_insert($comment) {
  // must confirm $comment->status

  // Create a new message, assigned to the node author, and add a
  // reference to the comment, so we can later use tokens related to that
  // comment.
  $message = message_create('comment_message_v2', array('uid' => $comment->uid));
  $wrapper = entity_metadata_wrapper('message', $message);
  // Reference field to the comment on the message
  $wrapper->field_comment_reference->set($comment);
  // Reference field to the node that was commented on
  $wrapper->field_node_comment_reference->set($comment->nid);

  // Let Message-subscribe save and send notifications.
  message_subscribe_send_message('comment', $comment, $message);
}